1. Field of the Invention
The invention relates to the field of xerography and somewhat more particularly to an improved fixing device in a printing or copying means for fixing toner images on support surfaces and to a solvent utilized in such devices.
2. Prior Art
Non-mechanical printing and copying means which operate in accordance with electrostatic principles are known in the art (for example see U.S. Pat. No. 3,861,863). In such printing or copying devices, toner images of the indica or characters which are to be printed are produced on a data carrier, for example, a web of paper. Such toner image production can be effected, for example, by printing charge images of the characters to be produced electrographically or electrophotographically on a photoelectric or dielectric subcarrier, for example a drum. These charge images are developed in a developer station using a toner. The toner images are then transferred to a data carrier in a reproduction station. Thereafter, the toner images are fused into or onto the data carrier in a fixing device, so that they attain a smear-free state.
Fixing devices which fuse the toner image into a data carrier are also known in the art (for example, see U.S. Pat. No. 3,861,963 or U.S. Pat. No. 3,324,791). In these fixing devices, the data carrier, after leaving the reproduction station, passes between two fixing rolls at least one of which is heated. The toner particles are fused into the data carrier by heat and pressure.
It is also known to fuse or fix a toner into a data carrier via solvent vapors (for example, see U.S. Pat. No. 3,049,810). In order to accomplish such toner fixing, a solvent vapor is produced which is capable of melting or plasticizing the toner on the data carrier, so that the toner can penetrate into the data carrier. The solvent vapor is directed to the data carrier provided with the toner images via a suitable device. Generally, such fixing device consists of a housing which contains a vaporization station and a data carrier guide which guides the data carrier through the housing. The fixing device is designed in such a manner that the least possible amount of solvent vapor can escape into the surrounding environment.
The solvents utilized for fixing purposes to produce a solvent vapor must exhibit a low degree of toxicity, should be non-inflammable because of the electrostatic charge associated with such devices, and should not form explosive gas mixtures. Heretofore, pure hydrocarbons and chlorinated and fluoridated hydrocarbons have been used as solvents. However, such solvents either exhibit inflammability with a relatively low degree of toxicity, or non-inflammability with a relatively high degree of toxicity.